There are a number of exercise devices which operate to allow a user to implement a foot action which follows a generally closed, curved path of travel which simulates running and/or walking. These devices are generally referred to as “elliptical” exercise devices. In a first generation of elliptical devices, the path of travel of the user's foot was predetermined and could not be varied while the device was in use. To the extent any variation or adjustment of foot path was desired, it would be accomplished by adjustment of the geometry of the components of the exercise device. A second generation of elliptical exercise devices is termed “adaptive” exercise devices and they are configured so that the vertical and horizontal components of a user's foot motion may be separately varied while the device is in use so as to allow for selectable control of the path of foot travel. Some such adaptive exercise devices are shown in U.S. Pat. Nos. 7,678,025; 7,507,184; 7,811,208; and 8,092,351. While prior art adaptive exercise devices do allow a user to adjust his or her foot path while actively exercising, it has been found that such adjusted foot paths still do not fully approximate a natural running and stepping motion.
As will be explained in detail hereinbelow, the present invention is directed to further improvements in adaptive exercise devices which allow a user's feet to travel along a path conforming to a natural running and stepping motion. As will be explained in detail hereinbelow, the system of the present invention is mechanically simple, reliable, and easy to use. These and other advantages of the invention will be apparent from the drawings, discussion, and description which follow.